Many chemical substances that have been regarded as safe are found to have the activity to disrupt the endocrine system and cause adverse effects in organisms. The wide presence of these kinds of chemicals in the environment has raised attention and concern worldwide. Because of the increasing reports of the estrogenic effects of these substances on male organisms, most of the research efforts have been directed to estrogen-like endocrine disruptors.
It is important to have a rapid, sensitive, economical, and quantifiable method to identify chemical substances that can mimic estrogen or interfere with the estrogen endocrine system, and that can assist in evaluating the biological effects of these chemical substances on organisms. Of the current available methods, in vitro cell line assays and in vivo transgenic fish assays have been investigated. Cell line assays can be rapid and sensitive, but they cannot provide information on toxicodynamic and toxicokinetic effects of test substances on organisms. Currently, transgenic fish assays can overcome some of the deficiencies of the cell line assays. However, current transgenic fish assays are limited in that they cannot be used to monitor endocrine disruptors in freshwater species, and they cannot be used in a marine environment.